New Mac-based security threats jumped in 2011, but still remain far below that of Windows PCs, according to a report by F-Secure Labs.

New Mac-based security threats jumped in 2011, but still remain far below that of Windows PCs, according to a report by F-Secure Labs.

A total of 58 unique variants were detected from April through December, according to the Labs' Threat Research team. Nearly half, 29, were Trojan downloaders, which F-Secure defines as a type of Trojan horse program that secretly downloads malicious files from a remote server then installs and executes them.

The F-Secure blog post didn't compare directly the 2011 results with the Mac's 2010 threat numbers, or with Windows' comparable numbers, except to assert that there had been an increase for Mac in 2011, but still very small compared to Windows. The company had not replied to a request for additional data as this story was posted.

The second most common threat category, with 15 detected, was backdoors, or remote administration utilities that are designed to slip past security mechanisms to secretly control a program, computer or network.

Also detected were seven Trojans, which F-Secure describes as non-replicating, deceptive programs that perform additional actions without the user's knowledge or permission and the same number of rogues, or fake antivirus software that uses false or deceptive tactics to pressure users into installing the code, which once loaded may not work as claimed.

F-Secure's research shows a kind of rollercoaster threat cycle for Macs last year, with threats rising and falling, peaking in June and again in October.